Field
This disclosure relates to a positive active material for a rechargeable lithium battery, a method of manufacturing the same, and a rechargeable lithium battery including the same.
Description of the Related Technology
In recent times, due to reductions in size and weight of portable electronic equipment, there has been a need to develop batteries for portable electronic equipment that have both high performance and large capacity. Batteries generate electrical power using an electrochemical reaction material for a positive electrode and a negative electrode. Rechargeable lithium batteries generate electrical energy from changes of chemical potential, when lithium ions are intercalated/deintercalated at the positive and negative electrodes.
Rechargeable lithium batteries include materials that reversibly intercalate or deintercalate lithium ions during charge and discharge reactions as both positive and negative active materials, and an organic electrolyte or a polymer electrolyte.
For the positive active material for a rechargeable lithium battery, composite metal oxides such as LiCoO2, LiMn2O4, LiNiO2, LiNi1-xCoxO2 (0<x<1), LiMnO2, olivine compounds, and so on have been researched. Manganese-based positive active materials such as LiMn2O4 and LiMnO2 are easy to synthesize, cost less than other materials, have excellent thermal stability compared to other active materials, and are environmentally friendly.
However, these manganese-based materials have relatively low capacity. LiCoO2 has good electrical conductivity, a high cell voltage of about 3.7V, and excellent cycle-life, stability, and discharge capacity, and thus is a representative material. However, LiCoO2 is expensive and can constitute more than 30% of the cost of a battery, and thus may cause a product employing such to lose price competitiveness.
In addition, LiNiO2 has the highest discharge capacity among the above positive active materials, but is hard to synthesize. Furthermore, since nickel is highly oxidized, it may deteriorate the cycle-life of a battery and an electrode, and may have a problem of severe self discharge and reversibility deterioration. Further, it may be difficult to commercialize due to incomplete stability.